Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$208.29	6.584%	$222.0038	$222.00	$222.00	$222.00
Purchase #2	$36.57	13.140%	$41.3753	$41.38	$41.40	$41.40
Purchase #3	$157.60	4.347%	$164.4509	$164.45	$164.45	$164.50
Purchase #4	$23.67	6.576%	$25.2265	$25.23	$25.25	$25.20
Purchase #5	$151.65	10.833%	$168.0782	$168.08	$168.10	$168.10
Purchase #6	$184.55	6.703%	$196.9204	$196.92	$196.90	$196.90
Purchase #7	$111.37	5.773%	$117.7994	$117.80	$117.80	$117.80
7 purchase totals =	$873.70		$935.8545	$935.86	$935.90	$935.90